Impurities are accumulated in a process if a production process of bisphenol-A (BPA) from phenol and acetone is used, and in order to prevent this, purge stream is present, and recovering technique of useful components therefrom is disclosed in U.S. Pat. No. 8,431,749 (applicant: Badger, et al.). By using this technique, an excessive amount of an aqueous solution of caustic soda (sodium hydroxide, NaOH) is injected to the purge stream, and phenol and acetone, which are raw materials of BPA may be recovered at a high temperature, with the advantage of a high recovery rate.
When examining the recovery process of phenol and acetone using such technique, the cracking reaction product of bisphenol-A residue is fed to a purification column, acetone is distilled and recovered first, a stream including phenol is transported to a neutralization bath together with an extracting agent, and the stream including phenol and the extracting agent are separated in an upper organic layer and a lower aqueous layer. Then, the extracting agent and phenol in the upper organic layer are respectively recovered via distillation, and remaining phenol in the lower aqueous layer is removed by extraction and discharged to a waste water treatment process.